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Wont Pull In Fourth

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jayjay

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Discussion starter · #1 ·
just fitted a 143 bbk, yx160 head and vm26 carb, the trouble im having is , it will pull like mad in 1st, 2nd and 3rd but put it in 4th and the revs will drop but it wont pull, dropped down 2 teeth on the rear sprocket and up 1 on the front but still no difference, anyone out there got and ideas
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#2 ·
jayjay said:
just fitted a 143 bbk, yx160 head and vm26 carb, the trouble im having is , it will pull like mad in 1st, 2nd and 3rd but put it in 4th and the revs will drop but it wont pull, dropped down 2 teeth on the rear sprocket and up 1 on the front but still no difference, anyone out there got and ideas
Image
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Hows jetting? Main ok? Not to lean/rich?
 
Discussion starter · #3 ·
it pulls great in the other gears and revs out no problem, could the jetting still be wrong and if so would it be only on the main jet, could i try moving the needle up or down a notch or would i have to change the jet
 
#4 ·
you probably don't have the horsepower to pull 4th. Try putting the stock sprockets back on. Racehead motors have weak low end and make all their power at high rpm. Even tho you have the stock sprockets, your top speed will be faster because the motor can rev more.



My friend has almost the exact same set-up, but he is running the stock head TB piston with a yx150 head. I think he needs a racehead piston to gain some more power. But on his bike, we actually are running a -1 front, and a +3 rear.
 
#6 ·
did u do anything to the head other than bolt it on ? i knw the v2 right outta the box u can make alot better by porting more and also throwing bigger cam or +r rockers. Idk about the yx head ?
 
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Discussion starter · #7 ·
head is fitted with a high lift cam but other than that just bolted it straight on with the 143 kit, had a 134 kit before that and have nt adjusted the jetting as it seems to run ok apart from the top end speed
 
#11 ·
you never posted your gearing, but it is usually the problem. klx trans ratio's are horrible. you are right that up in the rear gives better acceleration and less topspeed. but the problem is you dont have enough power to pull that tall 4th gear. the answer is going up in the rear or down on the front and the bike will rev out better in 4th (it wont drop rpms) it will also make all the gears closer together.
 
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